1. Field of the Invention
The present invention relates to a slow speed cruising control apparatus for controlling a cruising speed of an automobile.
2. Discussion of Background
FIG. 5 is a block diagram of such apparatus as disclosed in, for instance, Japanese Unexamined Patent Publication No. 247526/1986. In FIG. 5, a reference numeral 1 designates a slow speed cruising mode setting switch, a numeral 2 designates a slow speed cruising mode cancelling switch, a numeral 3 designates an accelerator pedal, a numeral 5 designates an actuator for driving a throttle valve 6, a numeral 7 designates an engine, a numeral 8 designates a speed sensor, a numeral 9 designates a range sensor for detecting the distance to an automobile going ahead of the automobile driven by a driver, a numeral 10 designates an alarm device, a numeral 11 designates a controller, a numeral 12 designates an accelerator pedal sensor for detecting a quantity of depression of the accelerator pedal 3, a numeral 13 designates a selector lever position sensor, a numeral 14 designates an engine revolution sensor, a numeral 15 designates turn signal switch, a numeral 16 designates a throttle valve opening degree sensor, a numeral 17 designates an accelerator switch and a numeral 18 designates a brake control device.
The operation of the above-mentioned conventional control apparatus will be described.
When the driver operates the slow speed mode setting switch to select a slow speed mode, a signal from the accelerator sensor 12 which detects a quantity of depression of the accelerator pedal 3 is received by the controller 11 and the throttle valve 6 is opened by the actuator 5 to thereby increase the output of the engine 7. The throttle valve 6 is not opened in proportion to the depression of the accelerator pedal but it is operated for opening (or closing) so that the revolution speed is lower than a certain level regardless of the quantity of depression of the accelerator pedal. When the accelerator pedal 3 is released from the foot, the throttle valve is closed and the brake control device 18 is actuated to thereby stop the automobile.
Thus, in the conventional slow speed cruising control apparatus, the automobile runs at a speed lower than a predetermined speed by operating only the accelerator pedal 3. Accordingly, it is convenient when the automobile has to be moved at a very slow speed at the time of a traffic jam. It is preferable for an automobile to have a sensor 9 to detect an obstacle so that a braking mechanism is automatically operated to stop the automobile, and the at the same time, to actuate an alarm device 10 when an obstacle is detected in the front of the automobile. The slow speed cruising setting mode is cancelled by turning off the slow speed mode switch 2 or generating a turn signal.
In the conventional control apparatus, however, the size of it is inevitably large and expensive because of the presence of the throttle valve and the braking mechanism although the automobile can be moved and stopped by operating only the accelerator pedal. Further, a fail-safe mechanism which ensures safety against the mulfunction of the brake control device is also expensive.